This invention relates to a rotary cutting unit for a self-propelled mower, such as a riding mower. More particularly, this invention relates to a rotary cutting unit having multiple cutting blades and a shock absorber for bi-directionally absorbing impact shocks on the outer side of the cutting unit.
Riding mowers are known for use on golf courses and the like for mowing a relatively wide cutting swath, i.e. a cutting swath in the 8xe2x80x2 to 12xe2x80x2 range. Such mowers have a traction frame that is self-propelled by a suitable power source, such as an internal combustion engine, carried on the traction frame. A seated operator is also carried on the traction frame for steering and operating the mower.
Mowers of this type often have multiple cutting units attached to the traction frame. Typically, these cutting units include a front cutting unit and two side cutting units. In addition, each cutting unit often includes at least two cutting blades rotatably mounted thereon. It is the combination of multiple cutting units, each having multiple cutting blades, that allows a very wide cutting swath to be cut.
The traction frame often includes a hydraulic traction system comprising a hydraulic pump powered by the engine. This hydraulic pump supplies pressurized fluid to hydraulic drive motors. Certain of these drive motors are operatively connected to at least some of the ground engaging wheels of the traction frame. Other of these drive motors are used to rotate the cutting blades on the cutting units.
In cutting units of the type used on these mowers, the cutting blades typically are not connected to one another by a timing belt, but are driven in an untimed manner by a V-belt. Thus, the cutting blades are arranged in a laterally overlapped, longitudinally staggered relationship. In other words, the orbit of one blade is longitudinally offset relative to the orbit of an adjacent blade, i.e. the orbit of one blade is in front of or behind the orbit of the adjacent blade, which allows the orbits of the two blade to slightly laterally overlap one another. This ensures that the blades cut a swath of grass without leaving an uncut strip of grass between the blades.
Similarly, the cutting units are themselves laterally overlapped and longitudinally offset relative to one another. The side cutting units trail the front cutting unit with the inner sides of the side cutting units laterally overlapping the outer sides of the front cutting unit. Again, this is to ensure that no uncut strip of grass if left between the cutting units.
A single hydraulic motor has been mounted on cutting units of this type to drive all of the cutting blades carried on that cutting unit. This motor has in the past been mounted on the cutting unit in a position which is longitudinally offset from the rotational axis of either blade. A single drive belt has been used extending from a drive pulley on the motor shaft around pulleys on each of the blade spindles to drive the cutting blades. This drive belt has a serpentine configuration as it passes from the motor pulley around the blade pulleys.
The life of the cutting unit drive belts described above is fairly short due to the serpentine belt configuration required to loop the belt around the motor drive shaft and the blade pulleys. This is a disadvantage because the short belt life means that such belts must be replaced more frequently than one would like. Moreover, significant side loads are imposed on the motor in this arrangement, requiring the use of a fairly expensive motor. Thus, there is a need in the art for a cutting blade drive system on cutting units of this type in which belt life is improved and in which side loads on the motor are minimized.
Another problem with cutting units of this type concerns impact shocks on the cutting units which arise during operation of the mower. This problem particularly affects the side cutting units. As the operator drives the mower forwardly or in reverse, it is not uncommon for the outer sides of the side cutting units to hit some obstacle, such as the trunk of a tree, a stake, etc. This is particularly true given the fact that these mowers often operate on golf courses where many such obstacles are present and where the mower is often driven quite close to such obstacles. In addition, this is also particularly true since the cutting swath is wide and it is difficult for the operator to always accurately judge the distance between the outer sides of the side cutting units and upcoming obstacles.
Mowers in the past have attempted to avoid damage from such impact shocks by allowing the side cutting units to yield or move slightly if an impact occurs against the outer side of the cutting unit. However, such units would typically yield only from shocks against the front of the cutting unit. Since these mowers are often operated in reverse, it is just as likely that a impact shock might arise from an impact against the back of the cutting unit. However, in prior art mowers, such impact shocks against the back of the cutting unit were not absorbed or yieldably resisted and could often result in damage to the cutting unit.
One aspect of this invention relates to a mower which comprises a traction frame capable of movement over the ground. At least one cutting unit is coupled to the frame. The cutting unit has at least two rotary cutting blades rotatably carried thereon for rotation in substantially horizontal cutting planes. Each cutting blade has a blade spindle rotatably journalled in the cutting unit. A single drive motor is carried on the cutting unit for rotating both cutting blades. The drive motor has a motor shaft that is coaxially arranged with one of the blade spindles and is coupled to the one blade spindle for rotating the blade spindle. The one blade spindle also has a first drive pulley coupled thereto. Finally, a drive belt transmits drive from the first drive pulley on the one blade spindle to a second drive pulley on the other blade spindle.
Another aspect of this invention relates to a mower which comprises a traction frame capable of movement over the ground. At least one cutting unit is coupled to the frame. The cutting unit is a side cutting unit operatively connected to the traction frame. The cutting unit can pivot relative to the traction frame about a substantially vertical axis. A shock absorber is provided for bi-directionally absorbing and resisting pivoting of the cutting unit about the vertical axis.